Procedures
1. Place dried chilies on a microwave-safe plate and microwave on high power in 15-second increments until pliable and toasted-smelling, about 30 seconds total. Transfer to a 2-quart microwave-safe liquid measuring cup or bowl. Add 2 cups chicken broth, cover with plastic wrap, and microwave on high power until gently simmering, about 5 minutes. Remove from microwave and set aside.
Alternative: Adjust oven rack to lower middle position and preheat oven to 275°F. Add dried chiles to large heavy-bottomed Dutch oven or stock pot and cook over medium-high heat, stirring frequently, until slightly darkened with intense, roasted aroma, 2 to 5 minutes. Do not allow to smoke. Remove chiles to small bowl and set aside.

2. At medium heat, add remaining two tablespoons oil and heat along with onions and garlic and cook, stirring frequently, until deep brown and just starting to burn, about 10 minutes. Add cumin/oregano and cook, stirring constantly until fragrant, about 30 seconds. Add chipotle chilis, vinegar, and remaining chicken broth. Scrape up browned bits from bottom of pan, simmer until reduced by about half, then transfer entire contents to the jar of a blender.

3. Add soaked chilis and their liquid to the blender. Start blender on low and slowly increase speed to high. Puree until smooth, about 1 minute. Set aside.

4. Place beef, bay leaves, and sauce into slow cooker for 8 hours on low.